Disposal of spent refinery caustic waste



Patented May 25, 1954 UNITED STATES PAN? OFFICE WAST Richard E. Knowlton Cuyahoga County, and Oil Company, tion of Ohio Warrensville Township, Ohio, assignor to The Stand- Cleveland, Ohio, a corpora- N Drawing. Application November 15, 1952, Serial No. 320,803

22 Claims. (01. 260627) This invention relates to a process for treating spent caustic petroleum refinery waste liquors to dispose satisfactorily of the waste.

In many petroleum refineries, gasoline blending stocks are treated with a strong caustic solution, which in some case may contain free sulfur dissolved therein. During this treatment corrosive mercaptans are eliminated from the treated asoline, while the caustic solution extracts undesirable sulfur compounds and cresylic acids. Cresylic acids is a general term used in the petroleum industry, and is used herein, to refer to the entire range of phenolic and related phenolic compounds found in crude petroleum, or formed therein during refining. The residual caustic will contain considerable amounts of these cresylic compounds usually as the sodium salts thereof and, since the gasoline stocks commonly contain hydrogen sulfide and other sulfur compounds, the caustic solution will also contain sulfide and other sulfur compounds after the treatment.

Disposal of waste caustic refinery liquor obtained by this treatment creates a serious problem because it is generally not possible to pump it into wells or run it into adjacent streams and waterways because of violation of local health and pollution laws. A stream is generally considered polluted if its phenolic content exceeds a maximum value set by law, if the combined biochemical oxidation demand (BOD) and chemical oxidation demand (COD) exceed the available dissolved oxygen in the stream, and if the odor is bad. Because the spent caustic leaves the refinery at temperatures of the order of 115 F., and because of the heat of dilution of the caustic with water, streams into which it is led are warmed considerably and this reduces the normal content of absorbed oxygen. If the temperature of the stream is, for example, 80 F., it contains about 7 parts of oxygen per million covered that by the treatment of the spent re- B finery caustic with an acid to a suitable adjustment of the pH and with a ferrous salt, the sulfides and other sulfur compounds may be precipitated together with a large portion of the phenolic compounds. The precipitate also entraps some of the phenolic compounds and phenolates and assists in their separation. The precipitate can be separated from the liquid by settling, filtering, centrifuging or by other conventional separation methods, and the liquid can then be discharged through the usual channels. If the liquid contains more phenol than it is desired to discharge, the liquid can be extracted with a hydrocarbon to remove the phenols. In practicing the invention, the spent refinery caustic is adjusted to a pH within the range of about 6.5 to 11.5 by the addition of a mineral acid, such as sulfuric, hydrochloric, etc. The sulfides in the caustic solution are precipitated by the addition of a ferrous salt such as ferrous sulfate, chloride, acetate, etc The sulfate is the cheapest and is preferred. If the pH is in the lower part of the range, more phenols will be separated than if it is in the higher part of the range. For example, if the original precipitation is carried out within the range of 6.5 to 7.5 phenols are precipitated along with the sulfides and hydroxides. The precipitate may then be removed in the manner described heretofore. The resulting solution may then be directed through the usual disposal channels. If the separation is at a pH in the higher part of the range and if it is desired to remove additional acid and the phenols in the filtrate can be extracted with the hydrocarbon solvent, such as petroleum naphtha.

Phenolic compounds which are present in the precipitate after filtration or other separation may also be recovered by treating the precipitate as petroleum naphtha.

The steel industry likewise is faced with a serious waste liquor disposal problem. The removal of oxide scale from certain steel products is an essential operation prior to further processing. Usually this is accomplished by immersing the steel in a bath of dilute sulfuric acid for a relatively brief period. The acid dissolves the scale together with some of the base metal, resulting in an accumulation of ferrous sulfate in the bath. This treatment is called "pickling and the liquor which results is called pickle liquor. Eventually the pickle liquor becomes .liquor to permit it to disappear ineffective and must be disposed of. Its disposal has been a problem for many years.

A variety of acids (sulfuric, hydrochloric, nitric,

hydrofluoric and phosphoric, individually and in combination) is employed, depending on the kind of product being treated, but sulfuric acid accounts for more than 90% of the tonnage pickled, and therefore disposal of sulfate pickle liquors presents the most serious problem. Spent sulfate pickle liquor normally has a composition ranging from 0.57 to 7% free sulfuric acid and from to ferrous sulfate when a batch pickler is used, while waste pickle liquor from a continuous pickler has from'2 to 7% free sulfuric acid and from 14 to 16% ferrous sulfate. The term pickle liquor as used in'the specification and claims is intended to refer to sulfate'pickle liquor having the aforementioned compositions, whether produced by a batch or a continuous pickling process of removing the oxide scale from steel.

The development of practical processes for the recovery of useful products from waste pickle liquor has engaged the attention of a largenumber of workers, and many processes have been proposed. "However, few of these processes have ever been operated successfully.

The easiest method is to recover ferrous sulfate and free sulfuric acid from the waste liquor. However, the demand for copperas in this country can be supplied by less than 4% of the pickle liquor produced by the steel industry alone. Moreover, copperas cannot be shipped Very far economically because ohm weight is water of crystallization. Both ferrous sulfate and sulfuric acid are low cost chemicals so that their recovery must be accomplished by the simplest possible process and equipment. However, hot dilute sulfuric acid is corrosive and it can be processed only at high equipment and mainte-' nance costs. 'Even when recovered it is not entirely satisfactory for reuse in pickling because of the tendency for impurities to accumulate. Where production of more valuable derivatives is investigated, similar difficulties are met.

Because of the apparent remoteness of any possibility that a feasible recovery process might be developed, it has become customary to discharge the spent pickle liquor into tide water, streams or lakes, either directly or through sanitary sewers. However, complaints against the pollution resulting therefrom has lead the industry to adopt other methods. The expedients most frequently employed have been lagooning the through solar evaporation and seepage into the earth or into slag dumps, or treating the liquor with lime. Neutralization of the liquor with lime is costly, and the by-product thereof is calcium sulfate which has little or no market value.

In accordance with an especially practical embodiment of my invention, the waste pickle liquor can be used as the source of the acid and the ferrous sulfate for treatment of the refinery wastes. This embodiment of my invention represents a particularly economical and satisfactory method for the joint disposal of two waste products, both of which present diflicult disposal problems. In practicing this embodiment of the invention spent pickle liquor is added to the spent caustic waste liquor. The preferred amount is that which will obtain the maximum precipitate. As a result the pH is thereby adjusted to between about 6.5 and about 11.5,and usually between 8.5 and 10.5. "In

the higher portions of this range the sulfurcom- Imaterial-the sulfides, removed before'the balance of the 4 pounds are precipitated but some of the phenolic compounds may be retained in solution and can be recovered by extracting with a hydrocarbon such as petroleum naphtha. If the addition of pickle liquor is separated into two stages so that at the first stage the pH ranges from about 8.5 to 11.5, the first precipitate will consist substantially of iron sulfides. Thereafter additional pickle liquor may be added to adjust the pH to about 6.5 to 7.5 at which point cresylic acids precipitate and may be removed. Further phenols can be removed from the liquid by extraction if desired. Phenolic compounds which are present in the precipitate after filtration or other separation may also be recovered by treating the precipitate to extraction .with a hydrocarbon solvent such aspetroleum naphtha.

When neutralizing to these higher pl-ls, however, there is some risk that the amount of iron in the pickle liquor may not be sufficient to precipitate all of the sulfides. For this reason, it is preferred to adjust the pH within the range of about 6.5 to 7.5 to assure the amount of iron in the pickle liquor'will precipitate all of the sulfur compounds such as iron sulfides, iron hydroxides, mixtures thereof, or as other insoluble salts. If any phenols remain in solution they can be extracted.

An amount of the pickleliquor is not added in excess of that which will give an additional precipitate. In thisway unprecipitated iron in the liquid is avoided. If the amount of pickle liquor brings the pH outside the ranges'mentioned, the pH can be adjusted, such as by the addition of a base such as lime, or an acid such as sulfuric.

It has been found that upon the addition of the pickle liquor with a spent refinery caustic a heavy flocculent precipitate occurs. This is particularly advantageous in that it adsorbs many of the troublesome compounds including certain of the phenolic-type compounds, which canbe separated when the precipitate is filtered or settled.

By the practice of the present invention then,

it is possible to recoveriron sulfides, oxides and hydroxides and the cresylic acid compounds. The most objectionable components'of each waste phenols, iron, etc.-are waste material is disposed of. The acid of the pickle liquor and the'alkali of the spent caustic solution are neutralized. The balance of the mixed waste material after removal of the precipitate and extractionof phenols isfound not to pollute streams when emptied therein.

The'following examples illustrate application of the'invention to typical caustic refinery waste liquors.

Example 1 A spent caustic refinery Waste liquor was treated having the following analysis:

Cresylic (phenolic) compounds 0.93% by wt. as phenol. Total sulfur 3.41% by wt. as S. Sodium polysulfide (NazSzs) 2.98% by wt.

To this caustic refinery waste was added sulfuric acid in an amount to bring the pH of the was then added a solution of ferrous sulfate in amounts until theaddition of additional ferrous sulfate solution did not precipitate. The precipitate which formed consisted of iron compounds including ferrous sulfide which was removed, by filtration. To the filtrate was added an additional amount of sulfuric acid to complete the neutralization to a pHof about 7.0. Any small additional precipitate was separated by filtration and the remaining liquor was disposed of through usual sewage channels.

Example 2 The process of Example 1 was repeated except that the filtrate at the end of the process having a pH of about twice with petrofrom the liquor before it was discharged to the sewer. The phenols can be recovered by distillation.

Example 3 The process of Example 1 was repeated and the precipitate which was separated in the filtration step was extracted with petroleum naphtha at room temperature to recover phenolic compounds therefrom.

Example 4 Example 5 Example 4 was repeated except that before discharging the liquor to the sewer it was extracted three times with equal parts of petroleum naphtha at room temperature for the purpose of further reducing the phenol content to 0.05% before discharging the liquor. The phenols can be recovered by distillation.

Example 6 The process of Example 4 was repeated and the precipitate which was separated in the filtration step was extracted with petroleum naphtha at room temperature to recover phenolic compounds therefrom.

Example 7 To 100 parts by volume of caustic refinery waste containing 4.8% cresylic compounds as phenols was added 26.3 parts of pickle liquor containing 29.3 .wt. per cent ferrous sulfate and 3.5 wt. per cent sulfuric acid to adjust the pH to about 9.4. A voluminous precipitate formed which was separated by centrifuging. Analysis showed the precipitate to consist largely of iron and sulfur compounds and some cresylic acids both in a precipitated and occluded form. The filtrate was further acidified with pickle liquor to a pH of 7 and filtered. It then contained 0.11% sulfur as sulfide and 1.13% cresylic acids as phenol.

Example 8 Example 7 was repeated except that the resid- 6 I ual liquor was extracted with petroleum naphtha before being passed to the sewers.

Emample 9 The process of Example 7 was repeated and the precipitate which was separated in the filtration step was extracted with petroleum naphtha at room temperature to recover phenolic compounds therefrom.

It will be apparent that the process of the invention accomplishes the mutual disposal of two spent waste liquors at very slight cost, the only additional materials required being mineral acids and petroleum naphtha, and even the use of these being optional. As a by-product of rendering these liquors innocuous, cresylic acid mixtures are recovered. These may be treated to separate phenols and cresols therefrom, if desired. The treated waste liquors are substantially free of sulfur compounds and cresylic acids, and therefore disposable in sewers in the ordinary Way, or even in streams and waterways without danger of polluting them.

Numerous changes and modifications may be made in the process without departing from the spirit thereof, as will be apparent to those skilled in the art. For example, the process may be carried out as either a batch or a continuous method.

I claim:

amount to precipitate at least a part of the sulfur compounds, and separating a resulting precipitate from the residual liquor.

2. The process of claim 1 in which the pH is initially adjusted within the range of 10 to 11.5 at the time of the precipitation with the ferrous salt, and after the separation of the precipitate, the pH of the filtrate is adjusted to about 6.5 to 7.5.

3. The process of claim 2 in which the resulting liquor at a pH of about 6.5 to 7.5 is extracted with a water-immiscible cresylic acid solvent to recover residual cresylic acids therefrom.

4. The process according to claim 3 in which the solvent is petroleum naphtha.

5. The process according to claim 1 in which the precipitate is extracted with a solvent for cresylic acids.

6. The process of claim 5 in which the solvent is petroleum naphtha.

7. The process adjusted within acids therefrom.

9. The process according to claim 8 in which the solvent is petroleum naphtha.

10. The process of claim 7 in which the precipitate is extracted with a solvent for cresylic acids.

11. The process of claim 10 in which the solvent is petroleum naphtha.

12. A process of treating spent caustic refinery waste liquors comprising sulfur compounds and cresylic acids, which comprises adding thereto spent pickle liquor produced in sulfuric acid pickling of ferrous metal, the said pickle liquor ,containing ierrous .su1fate- .and..sulfuric..acid,..in an amount sufficientto precipitate substantially all of the iron from the pickle liquor and to adjust the pH value of'the mixture to within the range of about"6..5 'to-about 11-.5 inorder to forums. precipitateuandseparating the resulting precipitate from the: residual liquor.

.13. The processor claim 12 in-which the amount of the pickle liquorwis sufiicientwinitially .dsozproduce-arpHawithin the: range of 10:to 11.5, land-4 after 1 the: separation; of" the: precipitatexzan ifidditiOD-fll! amount. ofnpickle liquorisadded tathe filtratentorproducesa pH". oiabout 6.51 to 7,5.

2.15.,The :1 process :of :claim 13 in which ;.the resulting liquor .2..extracted :awith oa wateriimmisciblecresyliozacid solvent t07':1BCOVB1-.'-12E8id -.ua1;-cresy1ic. acids-therefrom.

515.1 The'process according; to 'claimMain-which dvhe solvent is: petroleumznaphtha.

p16. :The :process ofi-claim;12.:inriwl'1ichthe ipreclpitate is: .extractedewitrr a-zs'olventiforccresylic .zacids.

.17. :The. processvof clahn .16.-in.wh1ch.thes01- ventnispetroleum. naphtha.

v18.;71he process .,of claim .12 in ,.which ..the

5 amount. .of-the pickle. liquonisv suflicient taproduce a .pH the. range ,of 6.5130 7.5.

v1,9. .The. process .of claim 18 in whichlthe.v resulting liquoris .extractedwith a water-immiscible .cresylic-.acid.=so1vent .tomecover residual cresylic acids.therefrom.

.20. The .processaccording to claim 19. inlwhich the solvent is petroleum naphtha.

.21. Yl he process of. claim,18 in which-the; precipitate is extracted with a solvent iorrcresylic acids.

22. The process of claim-21in which the solvent sis petroleum naphtha.

" Number References Cited the file omnis. patent UNITED? STATES PATENTS Name Date 2,635,120 "Alm .Apr. 14,1953 

1. A PROCESS OF TREATING SPENT CAUSTIC REFINERY WASTE LIQUORS COMPRISING SULFUR COMPOUNDS AND CRESYLIC ACIDS, WHICH COMPRISES ADDING THERETO A MINERAL ACID IN AN AMOUNT SUFFICIENT TO ADJUST THE PH VALUE THEREOF TO WITHIN THE RANGE OF ABOUT 6.5 TO ABOUT 11.5, ADDING A FERROUS SALT IN AN AMOUNT TO PRECIPITATE AT LEAST A PART OF THE SULFUR COMPOUNDS, AND SEPARATING A RESULTING PRECIPITATE FROM THE RESIDUAL LIQUOR.
 5. THE PROCESS ACCORDING TO CLAIM 1 IN WHICH THE PRECIPITATE IS EXTRACTED WITH A SOLVENT FOR CRESYLIC ACIDS. 